Session: COMP Poster Session:

Due to their computational efficiency, coarse-grained (CG) models are a promising alternative to all-atom (AA) simulations for simulating condensed soft matter. Bottom-up CG models, which rely on an underlying high-resolution model can, at least in principle, reproduce the properties of all-atom (AA) models that are observable at the CG resolution. Unfortunately, averaging over atomic details results in large entropic contributions to the interaction potentials, which severely limits their thermodynamic accuracy and state point transferability. In this work, we apply a dual potential approach to decouple the entropic and energetic components to the CG interaction potentials for CG models of ortho-terphenyl (OTP), a small, well studied, glass former. Specifically, we construct 1- and 3-site CG models both above and below its glass transition. We first employ force-matching to determine interaction potentials that accurately reproduce the structure of the AA model for OTP at each glass and liquid state point. We then employ an energy matching variational principle to determine the energetic component of the CG potential of mean force. The resulting energy operators quantitatively reproduce the energetics of the underlying AA model. Finally, we estimate the entropic contributions for each CG model. The resulting entropic functions successfully predict interaction potentials across the entire liquid temperature range, for both 1- and 3-site CG representations. The predictions in the glass phase are less accurate, however the predicted pair potentials still quite accurately reproduce the AA pair structure. Thus by explicitly considering the energetic and entropic components to CG interaction potentials, the dual potential approach provides a solution to both temperature transferability and energetic representability issues that plague bottom-up CG models.

Ryan Szukalo

Pennsylvania State University

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